1. Field of the Invention
The present invention relates to a digital versatile disk (DVD), and an apparatus and method for playing the DVD, and more particularly, to an audio DVD (hereinafter referred to as “DVD-Audio”) and an apparatus and method for playing the same.
2. Description of the Related Art
Recently, there has been developed a so-called video DVD (hereinafter referred to as “DVD-Video”), which has a considerably higher storage capacity than a laser disk (LD) so as to realize a significantly improved picture and sound quality. If the DVD is employed to store and retrieve only audio data, such DVD is called a DVD-Audio. The DVD-Audio provides means for storing and retrieving a large amount of audio data having a significantly improved quality compared to a compact disk (CD) or a digital audio tape (DAT).
The conventional CD stores an audio signal as linear pulse code modulated (PCM) audio data quantized into 16 bits by employing a sampling frequency of 44.1 KHz. The digital data stored in the CD is converted into analog signals by means of a CD player. The CD is much more convenient to use as compared to the previous microgroove phonograph record (LP), but is regarded as having a lower sound quality than the analog LP. This is because the audio signals are sampled at 44.1 KHz and quantized into 16 bits to be stored into a CD. Moreover, the audible frequency range may be over 20 KHz, and the dynamic range must be over 120 dB. In addition, the CD can only store audio signals of at most two channels, and therefore is impossible to store and reproduce the audio data concerned with multi-channel music. In these circumstances, there have been proposed various methods to improve the sound quality of the CD by increasing the numbers of the sampling frequency and the audio channels.
The DVD provides means to record video and audio data at high density. In this case, the video data is recorded in the MPEG (Moving Picture Expert Group) while the audio data is recorded in the linear PCM format, dolby AC-3 format, MPEG format, etc. Hence, the DVD-Video player is designed to reproduce both video and audio data recorded in a DVD-Video. Such a DVD-Video prepared to necessarily store video data is very uneconomical in view of the storage space when used for storing audio data only.
The audio data recorded in a DVD-Video has a much higher quality than that in a CD since the audio data of the DVD has a higher sampling frequency and larger numbers of quantization bits and channels than that of the CD. Namely, the DVD player reproduces high quality audio data in multiple channels.
The DVD is possible to transfer data at 10.08 Mbps at most. This makes it possible to reproduce data sampled at 192 KHz in two channels. This also approaches the maximum sampling frequency proposed as a prerequisite for the next advanced audio system at the Advanced Digital Audio Conference held in Japan in April, 1996. Thus, if audio data are recorded in a DVD-Audio, the DVD player may reproduce sounds of a significantly improved quality over that reproduced from the DVD-Video.